Convert bump maps to normal maps

[andybak]

Supercedes #534 - I've added an editor script that (hopefully) exports the normal maps exactly as Unity sees them internally.

[NicholasLiang]

The following is a screenshot on a simple material on a plane that use the old and the new normal map on a simple default material


I have an idea that may work. We can screen capture the normal map generated from Unity inspector and use that.

[andybak]

@NicholasLiang - let me double check something first.

[andybak]

@NicholasLiang Take a look now. I changed the algorithm and hopefully the data is correct..

[andybak]

Now we have "real" normal maps we can fix our gltf shaders to not apply an unnecessary bump to normal conversion.

The problem is that any code out there that has it's own copy of our shaders but makes use of the supplied texture maps will be wrong.

@mikeskydev - you know more about this side of things. Can you help me think this through? Does your three.js code use the textures but it's own copy of the shader code?

[andybak]

Marking this as draft. I am beginning to think we should keep both sets of normal maps. The old ones can go in the legacy GLTF folder and the new ones can go everywhere else.

[mikeskydev]

@andybak my three.js plugin ships with it's own set of textures (see https://github.com/icosa-foundation/three-icosa/blob/main/brushes/OilPaint-f72ec0e7-a844-4e38-82e3-140c44772699/OilPaint-f72ec0e7-a844-4e38-82e3-140c44772699-v10.0-BumpMap.png) so any changes to textures in unity shouldn't affect that side, but should test!

Also need to make sure the unity toolkit is sorted?

[andybak]

Also need to make sure the unity toolkit is sorted?

Yes. I can cover that.

How about Icosa upload? it seems to require the textures for a valid upload. (at least when I tested it the other week for the competition stuff)

[mikeskydev]

Oh! If Open Brush changed from the external tilt brush texture references to local references, that might have confused the URI rewriter. I can get that fixed.

[andybak]

I've merged this into #573 as it should really be merged at the same time as that.